Traffic control apparatus



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Dec. 16, 1941. J. L. BARKER 2,265,991

TRAFFIC CONTROL APPARATUS Filed Nov. 20, 1939 5 Sheets-Sheet 1 INVENTOR-Jomv L. fine/m? ATTORNEY Emcih (m BY Johw A. BAP/(5Q ATTORNEY ammo sis:mm.

ELEGTRXQSYEEAEWGu Dec. 16, 1941.

J. L. BARKER TRAFFIC CONTROL APPARATUS Filed Nov. 20, 1939 5Sheets-Sheet 3 INVENTOR Jar/Iv L 5/42/1EQ ATTORN EY EKEE'ST'MCSWN'AUNGQ1366- 1941- J. L. BARK ER TRAFFIC CONTROL APPARATUS Filed Nov. 20, 19595 Sheets-Sheet 4 INVENTOR JOHN L. flAR/fL-P BY ATTORN EY SGNAUNG.

- @eamh Dec 16, 1941 J BARKER 2,265,991

TRAFFIC CONTROL APPARATUS Filed Nov. 20, 1959 5 Sheets-Sheet 5 lNVENTORJOHN L BAP/{E2 ATTORN EY @[ELECTRlC Sit-3N AUNG,

seam iiliil Patented Dec. 16, 1941 TRAFFIC CONTROL APPARATUS John L.Barker, Norwalk, Conn., assignor to Automatic Signal Corporation, EastNorwalk, Conn, a corporation of Delaware Application November 20, 1939,Serial No. 305,233

26 Claims. (Cl

improved traffic control system or apparatus of I the trafiic actuatedtype, employing traflic detecting devices or detectors in theintersecting lanes, trafilc right of way signals at the intersection anda time controlled operating mechanism operated by the detectors todisplay the right of way signals to the several lanes successively fortime periods responsive to trafiic actuation of the respectivedetectors.

Some prior trafiic actuated signal systems have employed a resettabletiming device for timing a part of the right of way signal period for astreet under control of the traffic actuated detector of that street 'sothat actuations of the detector by vehicles approaching the intersectionduring the right of way period reset the timing device successively andcause it to repeat its time period, and thus prolong the right of waysignal display for such Vehicles. The time period for such a timingdevice is usually of only a few seconds duration so as to be not muchgreater than the average time spacing between successive vehiclesapproaching in moderately heavy traific, and thus if one or morevehicles are waiting on one street against a stop signal for example thego signal period on the other intersecting street will be terminated andright of way transferred to the first street in event that the time gapbetween approaching vehicles on such other street exceeds a reasonablevalue indicating that approaching trafiic using the go signal is sowidely separated that it would be more efiicient to transfer right ofway to the waiting trafiic on the opposite street.

In the traffic control system disclosed in the copending application,Serial Number 74,422, now 1 gressively reducing the time period of theresettable timing device for the right of way period on one streetresponsive to arrival of successive vehicles which increase the trafficwaiting on the other street.

The present invention provides a further improvement in systems of thisgeneral character in that the timing period of the resettable timingdevice determining the gap interval at which right of way may beterminated is progressively reduced during the right of way period ofone street by either one or both of two factors: (1) by the arrival of aseries of quite closely spaced vehicles or (2) by the passing of timefollowing the arrival of the first waiting vehicle on the other streetwhich does not have right of way.

The effect of reducing the time period of the gap interval timer is torequire moving traflic to maintain close spacing to retain right of way.

It will be appreciated by those skilled in the art of traffic signallingthat traflic flow has considerable variation from moment to moment aswell as hourly, daily and seasonal Variations. Such variations mayresult for example in having only one or two vehicles waiting on astreet at the beginning of the go signal period on a street and thenafter several seconds having a fairly closely spaced group of vehiclesarrive. It is therefore unsafe to employ a short time setting initiallyfor the resettable timer which establishes the gap interval which willrelease right of way, and the time ordinarily is started with a timeperiod providing a considerable margin above the gap interval of closelyspaced moving vehicles to avoid cutting off the right of way signal tooearly in the face of approaching trafiic. As the right of way periodcontinues however and the timer is reset by moving vehicles, anyvehicles waiting for right of way on the other street should not be heldtoo long and it is desirable to reduce the time period of the resettabletimer to take advantage of any appreciable time gap appearing in themoving trafiic which indicates that the volume of flow of the movingtraffic is decreasing.

The present invention provides apparatus for reducing the allowable gapinterval in accordance with the factors (1) and (2) outlined above, bothof which factors provide improved operation without the feature ofprogressive reduction of the gap interval in accordance with the numberof waiting vehicles disclosed in the copending application, SerialNumber 74,422, referred to above, but offer particularly markedefliciency and sensitivity to slight changes in flow of heavy trafiic incombination with this feature of the said copending application. Theinvention is described and illustrated in its preferred embodiment inconnection with the apparatus of the copending application and is alsoindividually described.

In systems of this general character it is the usual practice to providea maximum limit timer for terminating right of way on one street after acertain maximum period of substantial continuous moving trafiic on theone street if trafiic is waiting on the other street, and the presentapparatus includes this feature but it is one aspect of the inventionthat the reduction of the gap interval timing period may be made sopronounced as to go below the minimum possible spacing of moving trafiicand thus force release of right of way after a maximum time period inlieu of the use of a separate maximum limit timer.

Also in systems of this general character in which vehicles approachingthe intersection on a go signal extend the period of display of saidsignal, the go period is preferably divided into at least two parts thefirst part being identified ordinarily as an initial interval orstarting interval for the purpose of enabling accumulated waitingtraffic to get into motion and the second part comprising a unit timeextension interval which is repeatedly reset by vehicles in the streamof moving traflic. The unit interval of the second part is variouslydesignated in the art as a vehicle protection period, right of wayextension period, gap limit interval or vehicle interval. The first partwill be referred to herein uniformly as the initial interval and theunit extension period of the second part will be referred to herein asthe vehicle interval.

In the present system as in prior types of vehicle actuated systems theactuation of traffic detector in a traffic lane in which the stop signalis being displayed causes the right of way to be transferred to thatlane at the first opportunity. If there is no traflic entering theintersection from the lane in which the go signal is being displayed acaution signal is usually immediately displayed in said lane and after ashort period the right of way is transferred to the lane in which thestop signal was being displayed.

If traflic is moving in the lane wherein the go signal is beingdisplayed the actuation of the traflic detector in the lane in which thestop signal is being displayed causes the right of way to be transferredthereto at the first break of a predetermined time in the said movingtraffic. If no such break occurs in said moving traific the right of waywill be transferred at the end of a predetermined maximum period usuallyprovided by a different timing element.

This system, like some previous traflic actuated systems is arranged sothat the timing of the initial interval, the first part of the goperiod, I

can, before the beginning of said initial interval," be preadjustedbetween a predetermined minimum value and a predetermined maximum value,by successive actuations of the trafiic detector in the lane in whichthe stop signal is being displayed so that when said lane shall next begiven the go signal the initial interval of said go signal displayperiod will be timed in conformance with the volume of the trafiicwaiting in said lane, to the end that a large number of waiting vehicleswill be granted a longer initial interval than will be granted to asmall number.

In this system the traflic detectors can be located at a distance fromthe intersection customary in the older types but it is entirelyfeasible, especially if the variable initial interval is employed, tolocate them considerably farther from the intersection (two or threehundred feet or more for example) thereby facilitating the counting oflarger numbers of waiting vehicles which will increase the effectivenessof traflic approaching a stop signal in controlling the signal timing.

With the system adjusted to give a pronounced reduction of the vehicleinterval after the accumulation of a certain amount of trafficapproaching a stop signal a considerable degree of coordination betweenadjacent intersections can be obtained solely by the pressure of trafficitself without any electrical interconnection since the effect of such agroup of vehicles approaching successive intersections equipped withthis system will be to so reduce the vehicle interval for cross trafficat each intersection as at any time subsequent to the cross streetinitial interval to practically seize the right of way at intersectionafter intersection thereby favoring uninterrupted progress to asufficiently large compact group of vehicles.

Cross traffic will however be protected against unreasonableinterruption since the cross street initial interval is timed in advancein accordance with the number of vehicles waiting on the cross streetand is not reducible by main highway traffic, and in addition either amaximum limit to right of way on the main highway or a reduction of themain highway vehicle interval by accumulation of waiting cross streettraific, or both, serve to protect the cross street traflic.

It will be appreciated that traffic is often heavier inbound toward thecentral area of a city in the morning and heavier outbound in theafternoon, and that in such cases the automatic natural coordinationeffect above noted with this invention will be particularly pronouncedon the main traffic arteries.

It is a general object of the invention to provide an improved streettrafiic control apparatus that is very closely responsive to changes inthe volume of traffic so as to transfer right of way to waiting trafficon one traflic lane upon occurrence of a relatively small gap in movingtraffic on an interfering traffic lane.

It is another object to provide an improved system in which vehiclesawaiting the right of way in one lane will facilitate yielding the rightof way from the other roadway by reducing the time allotted to eachvehicle entering the intersection from such other roadway.

It is another object to provide an improved apparatus in which transferof right of way from moving traffic on one lane to waiting traffic on aninterfering lane is controlled a traffic actuated timing mechanism whichestablishes a maximum time limit for the spacing between vehicles in themoving traffic and in which such spacing time limit is adjustedresponsive to variations in the actual time spacing of vehicles in themoving traffic as determined by actuations of the timing mechanism bytraffic.

It is a further object of the invention to provide an improved apparatusin which transfer of right of way from moving traffic on one lane towaiting traffic on an interfering lane is determined by the time spacingof vehicles in the moving traffic lane reaching a maximum time spacinglimit which is established by a timing device and which is reducedresponsive to closely spaced vehicles in the moving traflic.

It is a further object of the invention to provide an improved apparatusin which transfer of right of way from moving traflic on one lane towaiting traflic on an interfering lane is determined by the time spacingof vehicles in the moving traflic lane reaching a maximum time spacinglimit which is established by a timing F3. yiLECTRlC SEGNAUNG;

device and which is reduced progressively responsive to passage of timewhile trafiic is waiting on the interfering lane.

It is another object to provide improved trafiic right of way controlapparatus for interfering trafiic lanes having means actuated by trafficin the lanes and a timing device controlling transfer of right of wayfrom one lane to the other lane at the end of its timing period andarranged to reset to repeat its time period responsive to operations ofthe traffic actuated means in said one lane having right of way, andalso being arranged to have its time period reduced responsive toclosely spaced such actuations and responsive also to passage of timeafter the first actuation by traffic waiting on the other lane nothaving right of way.

It is another object of the invention to provide improved trafficcontrol apparatus having a timing mechanism controlling termination ofright of way at the end of its time period and arranged to be reset torepeat its time period responsive to vehicles approaching theintersection on one lane having right of way, and in which the length ofthe timing period of such device is reduced by a combination of factorsincluding the amount of trafiic waiting and the length of time traffichas been waiting for right of way on the other trafiic lane and closespacing of vehicles on the lane having right of way.

An embodiment of the features of the invention will now be describedwith reference to the drawings in which Figure 1 is a schematic planview of an intersection showing the location of traific detectors,signals and operating mechanism of a trafiic control system employingthe present invention.

Figures 2 and 3 combined represent a schematic circuit diagram of atraflic control system employing the present invention in combinationwith one form of the apparatus of the copending application, SerialNumber 74,422, new United States Patent Reissue 21,377.

Figure 4 is a schematic circuit diagram of the part of the apparatus ofFigs. 2-3 providing adjustment of the time period of a maximum vehiclespacing limit timer responsive to the actual spacing of traflic movinghaving the right of way, in accordance with one feature of the presentinvention.

Figure 5 is a schematic circuit diagram of the part of the apparatus ofFigs. 2-3 providing adjustment of the time period of a maximum vehiclespacing limit time responsive to passage of time, in accordance withanother feature of the present invention.

Figure 6 is a plan view of a group of adjacent intersections equippedwith this system showing one example of the location of signals, trafficdetectors and timer housings.

Referring now to Fig. 1 right of way signals [0 are shown at the centerof the intersection of two streets NS and EW, traffic detectors l2 arelocated at some distance from the intersection on the NS street andtraific detectors l3 are similarly located in the EW street. Thesedetectors are located preferably in position to be actuated only bytrafiic approaching the intersection but may if desired be of adirectional type such as disclosed in Patent Number 2,077,924 granted toCharles D. Geer and John L. Biach on April 20, 1937, for example so asto be actuated only by trafiic approaching the intersection. The controlmechanism II is illustrated sche- Search matically as connected to thedetectors and signals.

Any type of visual or audible signal can be used in this system but thecustomary red, yellow and green trafiic lights are preferable inasmuchas motorists and pedestrians are now generally familiar with thesignificance of these colored lights. The signals are illustrated inFig. 1 as grouped at the center of the intersections but it will beappreciated that they may also be located at other appropriate points atthe intersection either grouped or separated.'

The trailic detectors may be of any desired form such as a mechanicalswitch in which the pressure exerted by the weight of a passing vehicleflexes a resilient plate to make a contact, or an energy beam isdirected across a trafiic lane so as to be interrupted by trafiicapproaching the intersection. A common form of the latter type is alight beam directed across a trafiic lane with a photo electric cellarranged as a receiver. Still another type of detector is anelectromagnetic device in which the vehicle disturbs a magnetic fieldand thereby operates a relay in the control. Any of these or other typesof traffic detectors such as a push button for use of pedestrians willoperate satisfactorily in this system.

Examples of suitable forms of the mechanical switch type of traificdetector are disclosed in Patent Number 1,928,472 granted to H. A.Wilcox, Jr. on September 26, 1933, and Patent Number 1,950,490 grantedto C. D. Geer and E. D. Stirlen on March 13, 1934, for example.

The operating mechanism ll of Fig. 1 controls the signals undercooperative control by timing devices included in the mechanism and bythe traffic detectors.

A preferred embodiment of this mechanism employing the invention incombination with one form of the apparatus of the aforesaid copendingapplication, Serial Number 74,422, is shown in Figs. 2 and 3. Thisembodiment employs a multiple rotary line switch or stepping switch andgrid controlled discharge tubes and because of the sharply definedbreakdown voltage of this type of tube great accuracy is possible intiming the Various intervals. Moreover since their grid potentialdetermines their breakdown voltage these tubes can be adjusted tocompensate for variations in tube characteristics by connecting the gridto an appropriate potentiometer tap when tubes are replaced. Thus theaccuracy of the timing of the various intervals can be maintainedindependent of variation of tube characteristics in differentreplacement tubes.

The stepping switch shown in Figs, 2-3 has eight positions. A steppingswitch of more than eight positions can be used as an eight positionswitch if desired by providing rapid stepping through the extrapositions in accordance with well known methods.

It will be appreciated that a multiposition rotary camshaft and camoperated switches and associated step-by-step driving mechanism could beemployed in lieu of the rotary stepping switch shown for purpose ofillustration.

A complete cycle of operation of the signals by the stepping switchincluding right of way periods for the respective NS and EW streets andamber change periods for the same is outlined in the chart at the bottomof Fig. 3, showing the eight stepping switch positions and thecorresponding signal indications and the names given to the severalintervals in the respective stepping switch positions to more readilyidentify their functions.

In Figs. 2 and 3 negative A. C. power is supplied through the wiredesignated by a minus sign enclosed in a circle and extending verticallythrough substantially the middle of the figures. At the bottom of Fig. 3this wire is identified as grounded A. C. Positive A. C. is suppliedthrough wires designated by a plus sign in a circle at the right andleft sides of these figures and positive D. C, is designated by a plussign in a square at the right and left sides of these figures. NegativeD. C. power is designated by a minus sign in a square at the middle ofthe top of Fig. 3 and it will be noted is maintained at a relativelymore negative potential than the negative A. C. by means of thepotentiometer PZ6-PZ'|.

The six contact banks of the stepping switch are shown somewhat to theright of the vertical negative power wire near the middle of the figuresand are identified as banks SBI to SE6 respectively with each of thecontacts numbered l to 8 to correspond with positions I to 8 of thestepping switch. The several wipers WI to W6 inclusive are shown inposition between positions 4 and 6 and are arranged to be operated inunison across the contacts of their associated contact banks from oneposition to another by operation of the stepping switch driving magnetDM shown in the lower left part of Fig. 3.

The remainder of the apparatus represented on the part of Fig. 2 to theright of the negative power is in general effective to cooperate withthe apparatus of Fig. 3 to call the right of way to the EW lane and tohold the right of way thereon. In like manner the apparatus representedby that part of Fig. 2 to the left of the power wire is effective tocooperate with the apparatus of Fig. 3 to call or hold the right of wayon the NS lane.

At the top of Fig. 2 ar shown the two sets of signals representing thecustomary green, yellow and red lights, numbers Z48 to Z50 beingdisplayed to the EW traiiic whereas numbers Z45 to Z4! are displayed tothe NS trafiic.

The trafiic detectors located respectively in the NS and EW lanes arerepresented by Z5l and Z52. Relay EZ is responsive to actuations ofdetector Z5! and relay FZ operates in response to actuations of detectorZ52.

The operation of relay FZ starts a sequential operation which calls theright of way to the EW lane and when the right of way has been given tothe EW lane, operation of this relay tends to hold it there. Similarlyrelay EZ operates to call and hold the right of way on the NS lane.

By opening or closing switches Z68 and Z69 the apparatus can be causedto normally operate as a reverting, arterial or floating system. The010- sure of both switch Z68 and switch Z69 will in the absence oftraffic cause the right of way to normally revert periodically from laneto lane. This system of operation is commonly called the revertingsystem.

If switch Z68 is closed and switch Z69 is open a NS arterial systemresults in which the right of way will normally remain on the NS laneuntil called by trafiic to the EW lane. After the EW trafiic has clearedthe intersection the right of way will automatically revert to the NSlane. In the event of continuous EW traffic under the above system theright of way will periodically revert to the NS lane, and remain thereas long as NS trafiic may require it up to a predetermined limit.

If switch Z69 is closed and switch Z68 open the system will operatearterial EW under which system the EW lane instead of the NS lane willbe the artery. The right of way will normally remain on the EW laneuntil called by trafiic to the NS lane, from which lane it will revertto the EW lane when the NS trafiic has cleared the intersection or hasheld the right of way on the NS lane for a predetermined time.

If switches Z68 and Z69 are both open the apparatus will operate as afloating system under which the right of way will normally remain on thelane to which it was last called until trafilc on the cross lanerequires it.

Under all of these systems of operation trafhe on each lane can hold theright of way up to' a predetermined period against waiting traffic inthe cross lane and in addition automatically put in a call for thereturn of the right of way to the lane from which it is beingtransferred if at the time of such transfer a vehicle interval has beeninitiated by a detector actuation in said lane within a predeterminedtime prior to said transfer of the right of way or if the vehicleinterval prevailing thereon at the time of such transfer has by waitingcross trafiic been reduced to less than a predetermined magnitude.

The various time intervals are timed by several timers including aninitial interval timer, a maximum timer, a variable vehicle intervaltimer and a normal vehicle interval timer. The several timers are of thestatic or electronic type employing the time required to charge acondenser slowly through a control resistance from a D. C. power supplyto the breakdown voltage of a gaseous discharge tube which thereuponpasses current to operate a relay. The discharge tubes employed in thepresent embodiment are of the three electrode type in which the negativegrid bias controls the breakdown voltage to initiate conduction in theanode-cathode circuit, the breakdown voltage being substantiallyproportional to the grid bias over a considerable range.

The initial interval timer has its time interval adjusted in accordancewith accumulated waiting trafrlc for timing the initial intervals inpositions l and 5 but is used as a definite interval timer also in therest positions 2 and 6 and in the amber positions 4 and 8. For timingthe initial interval its time period is adjusted substantially inaccordance with the number of waiting vehicles by charging a condenserduring the initial interval from an initial voltage predetermined by thenumber of such waiting vehicles.

When the stepping switch is in its trafiic timed positions 3 or 1, threetimers run concurrently. One of these, the maximum timer, is not subjectto vehicle control. The other two, the variable vehicle interval timerand the normal vehicle interval timer, are both subject to reset thruplate condenser discharge by trafiic actuations in the lane in which thego signal is being displayed. Hence their periods start simultaneouslyafter each such reset. The variable vehicle interval timer is subjectalso to partial control by waiting cross traflic which decreases itsoperating period. The normal vehicle interval timer on the other hand isnot afiected by cross trafiic.

The Variable vehicle interval timer period is decreased by waiting crosstrafiic thru having the grid potential of the tube timing this periodrendered less negative by waiting cross traific thus causing said tubeto become conducting at a lower plate voltage which correspondingly de-ELECTRIC SIGNALING.

creases the period required for charging the plate condenser to thislower voltage and so decreases correspondingly the variable vehicleinterval. Hence the larger the amount of waiting cross traffic theshorter the variable vehicle interval will be. From the abovedescription it can be seen that the variable vehicle interval timer ineffect balances the increasing pressure to take the right of way exertedby accumulating waiting traffic on one street against the right of wayretaining efiect exerted by moving trafiic on the other street. Thelatter effect may be termed the holding power and is proportionate tothe frequency with which said moving traffic resets the variable vehicleinterval timer.

If the variable vehicle interval is decreased to less than the normalvehicle interval right of way will be yielded by action of the variablevehicle interval timer when traflie ceases to approach the intersectionfrom the lane in which the go signal is being displayed. The variablevehicle interval timer is arranged to automatically put in a returnright of way call whenever it operates. If there is little waiting crosstraffic and consequently the variable vehicle interval is not reduced toless than the normal vehicle interval, the normal vehicle interval timerwill operate first to yield the right of way. The operation of thistimer does not put in a return right of way call. Hence a right of wayrecall will be automatically put in if the vehicle interval at the timeof right of way transfer has been reduced by waiting cross traffic toless than a predetermined period. The predetermined period referred tois the normal vehicle interval timer period.

If repeated trafiic actuations in the lane in which the go signal isbeing displayed continually reset both of the vehicle interval timersthus preventing either of them from operating, the right of way will betransferred by action of the maximum timer, which is effective in thetraffic timed stepping switch positions 3 or I. A return call for theright of way is automatically put in by this timer whenever it operates.

The fact that the maximum timer operates and the normal vehicle intervaltimer does not operate indicates that the normal vehicle interval timerwas reset by a traflic actuation less than the time period of saidnormal vehicle interval timer, i. e. less than a predetermined timebefore the transfer of the right of way.

The stepping switch will remain in either of its two rest positions 2 or6 unless the system is set for normally arterial or reverting operationor unless a cross trafiic call is put in by a cross lane detectoractuation.

Referring to Figs. 2 and 3 the following points will be noted.

The stepping switch contact banks, designated as SBI to SE6 inclusive,are shown in Figs. 2 and 3 to the right of the grounded power wire whichextends from the bottom to the top of both figures just to the left ofthe center. The stepping switch driving magnet, designated as DM, isshown in the lower left corner of Fig. 3. This magnet DM drives thewipers WI to W6 in unison over the banks SBI to SBG respectively. Besidit is a rectifier used to supply D. C. for the driving magnet coil.

The signals shown at the top of Fig. 2 are controlled by relays ALR andBLR. The apparatus to the left of the grounded power wire in Fig. 2 isin general efiective to cooperate with the apparatus of Fig. 3 to calland hold the right of way on the NS lane whereas that to the right ofthe grounded power wire similarly cooperates with the apparatus of Fig.3 to call and hold the right of way on the EW lane.

Relay AM is energized thru contacts in stepping switch bank SBZ when thestepping switch is in positions 2 and 3, the NS rest position and the'NS trafiic timed positions respectively. Right of way can be called tothe NS lane by the deenergization of relay AM which can occur inresponse to a NS traffic actuation when the right of way is not on theNS lane. Furthermore if the right of way leaves the NS lane thru actionof the maximum timer relay MXR or the variable vehicle interval timerrelay VVR the relay AM will be deenergized thus putting in a call forthe return of the right of way to the lane from which it is beingwithdrawn, in this instance the NS lane. It will be remembered that theplacing of a return call has been mentioned as a function of both themaximum timer and the variable vehicle interval timer.

If on the other hand the right of way is'transferred from the NS lane byaction of the normal vehicle interval timer relay YR, relay AM will notbe deenergized but will remain locked in thru subsequent stepping switchpositions unless it is deenergized by the actuation of a NS vehicledetector in order to call the right of Way to the NS lane.

Relay BM performs similarly with respect to the EW lane, being operatedthru contacts of stepping switch bank SBI when the stepping switch is inposition 6 or I, the EW rest and trafilc timed positions respectively.It is deenergized to put in an EW return call as the right of way iswithdrawn from the EW lane if said withdrawal is caused by the maximumtimer relay MXR or the variable vehicle interval timer relay VVR butremains locked in if said withdrawal of the right of way is caused bythe operation of the normal vehicle interval timer relay YR. Relay BM insubsequent stepping switch positions can be deenergized by action ofrelay FZ in response to an actuation of EW detector Z52 in order to callthe right of way to the EW lane.

Relay AR which is energized by stepping switch contacts of bank SBI instepping switch positions I, 2, 3 and 4, the NS right of way and amberpositions, energizes signal relay ALR and completes certain of thetiming condenser circuits as will later be explained in detail.

Relay BR is energized in stepping switch positions 4, 5, 6 and I tosimilarly energize signal relay BLR and connect other timing condensercircuits.

The maximum timer, effective in the NS and EW trafiic timed steppingswitch positions 3 and I to limit the time during which moving trafiiccan hold the right of way against waiting cross traffic includes relayMXR, plate condenser KMX and tube MXT.

The variable vehicle interval timer includes relay VVR, tube VVT, platecondenser KVV and grid condensers KGNS and KGEW. It times the variablevehicle intervals in stepping switch positions 3 and I, the charge incondensers KGNS and KGEW being afiected respectively by EW and NStraffic so as to decrease the variable vehicle interval in the NS and EWlanes respectively in accordance with the amount of waiting crosstrafiic as previously mentioned.

Relay YR, tube YT and condenser KV c0- operate to time the normalvehicle interval, with the stepping switch in position 3 or I, whichinterval starts simultaneously with the variable vehicle interval aftereach vehicle actuation in the lane having the go signal. The timing ofthe normal vehicle interval it will be remembered is not afiected bywaiting cross traflic whereas the timing of the variable vehicle interalis afiected by waiting cross traffic.

Relay YR and tube YT cooperate with other condensers in difl'erentstepping switch positions to time other intervals as follows. The NSinitial interval, stepping switch position I, is timed by relay YR, tubeYT and condenser KINS, the charge in the condenser KINS at the beginningof this interval having been predetermined by NS vehicle actuationsoccurring during or before the preceding display of the NS stop signalin order to time the NS initial interval in accordance with the amountof NS trafiic waiting at the beginning of the NS go signal displayperiod.

Relay YR and tube YT cooperate similarly with condenser KIEW to time theEW initial interval, stepping switch in position 5, in accordance withthe amount of EW traflic waiting at the beginning of the EW go signaldisplay period, the starting charge in condenser KIEW beingpredetermined in accordance with the amount of said waiting EW traffic.

The same relay and tube cooperate with condenser KY to time a minimumperiod during which the stepping switch remains in its rest positions 2and 6 in order to ensure that when the go signal is given to a lane itwill remain there for a reasonable minimum period. At the expiration ofsaid minimum period the: right of way will be transferred to the otherlane only if traflic or normal reversion requires it, hence the namerest position. This same group times the NS and EW amber or warningperiods, stepping switch in position 4 and 8 respectively.

To more completely describe the features of the embodiment of myinvention shown in Figs. 2 and 3 I shall now explain its operation thrua complete signal and stepping switch cycle beginning in the NS initialinterval when the right of way has just been given to the NS lane,stepping switch in position I.

In this stepping switch position relay AR is operated, current beingsupplied thru the circuit starting at grounded power thence thruposition I of stepping switch bank SBI to relay AR to A. C. plus power.Relay AR when operated causes signal relay ALR to be energized thru thecircuit starting at A. C. plus, thru relay ALR, wire 202 to contact earlof relay AR thence to grounded power. Relay BR is deenergized instepping switch position I, its circuit being open at stepping switchbank SB2. Hence signal relay BLR is deenergized since its operatingcircuit includes contact brI of relay BR.

Wipers WI and W2 are of the bridging type so that the relays energizedthru them at their respective contact banks SBI and SB2 will not bedeenergized as the stepping switch moves from one position to the next.

With relay ALR operated and relay BLR unoperated the NS go signal Z45will be illuminated thru the circuit beginning at grounded power, thrusignal Z45 thence to contact bZrI of relay BLR thence to contact alr4 ofrelay ALR and to A. C. plus power. The EW stop signal Z50 is illuminatedthru the circuit from grounded power to A. C. plus power includingsignal Z50 and contact alr2 of relay ALR. The circuits to the other foursignals are incomplete in stepping switch position I.

Explanation of the relay AM coil circuit will be helpful at this pointas an aid in following this step-by-step description of the systemoperation.

Relay AM has an operating circuit from grounded power thru wiper W2,stepping switch bank SB2 positions 2 and 3, wire 206, 205, coil of relayAM, wires 204, 216, 211, 221, contact dm2 to A. C. plus. It has inaddition a holding circuit from grounded power thru contact cal of relayEZ, contact amI of relay AM, wire205, coil of relay AM, wires 204, 216,21! to contact am2 of relay AM, wire 219, contact macrl of maximum timerrelay MXR, contact curl of variable vehicle interval timer relay VVR,thence to A. C. plus power.

In stepping switch position 2 relay AM is energized thru the operatingcircuit described above. That part of the operating circuit supplyingcurrent to the left side of the coil remains complete from the time thestepping switch enters position 2 until it leaves position 3 after whichit is broken at bank SE2. Wiper W2 is of the bridging type to insurecontinuity of the above circuit as the stepping switch moves fromposition 2 to 3.

That part of the operating circuit energizing the right side of the coilof relay AM will be opened at contact dm2 as the stepping switch movesfrom position 2 to 3. However that portion of the holding circuitparalleling the last named part of the operating circuit remains intactto supply relay AM with A. C. plus power While contact dm2 is openduring the stepping switch movement. From the above description it canbe seen that relay AM is always energized when the stepping switch is inposition 2 or 3 and when it is moving from position 2 to position 3.

The functioning of relay AM in subsequent stepping switch positions willbe explained as the circuit operation in each position is considered.

The NS initial interval is timed by relay YR, tube YT and condenserKINS. During this interval condenser KINS is connected to relay YR andto the plate of tube YT thru the circuit going from grounded power tocondenser KINS to wires 282, 290, 284 to stepping switch bank SE3position I to Wiper W3, wires 224, 225 to coil of relay YR, wire 260 toplate of tube YT. During the NS initial interval condenser KINS ischarged thru the circuit starting at grounded power, to condenser KINS,wires 282, 290, 284, to stepping switch bank SB3 position I to wiper W3,wires 224, 223 to timing resistance RZ5, wire 2I4, to stepping switchbank SE4 position I, to wiper W4, wire 225 to stepping switch drivingmagnet contact dmI to D. C. plus power. When condenser KINS is chargedto a predetermined voltage the tube YT will break down, i. e. becomeconducting, thereby connecting relay YR to ground and allowing condenserKINS to discharge thru relay YR which will therefore operate and thrucontact yrI connect the rectifier associated with the driving magnet DMto power thus energizing the stepping switch driving magnet DM whichwill thereupon move the stepping switch into its next position. To varythe duration of the NS initial interval the rate at which condenser KINSis charged in stepping switch position I can be adjusted by regulatingthe variable charging resistance RZ5.

It has previously been stated that the initial interval is timedsubstantially in accordance with the amount of waiting cross trafiicthru having the charge in the initial interval timing tarmacelegance.

which man condenser at the beginning of the initial intervalpredetermined by such waiting cross trafiic. In this connection considerspecifically the NS initial interval during which the stepping switch isin position I.

While the stepping switch was last in positions 2 and 3 relay AM wasenergized as has been previously explained. Therefore in these twostepping switch positions condenser KINS was charged thru the circuitfrom grounded power to condenser KINS, wires 282, 28!, contact a.m4 ofrelay AM, to resistance RZI5, wire 228 to potentiometer resistance PZ'I.The maximum voltage to which condenser KINS can be charged by thiscircuit is predetermined by the point on the potentiometer PZ'I to whichwire 228 is attached. The rate at which condenser KINS is so charged canbe regulated by the adjustment of variable resistance RZI5.

While condenser KINS was being charged in stepping switch positions 2and 3 as explained above and during succeeding intervals up to the EWamber period immediately preceding the next NS initial interval, i. e.while the stepping switch is in positions 2, 3, 4, 5, 6 and l, thecharge of condenser KINS is subject to the removal of an increment ofcharge by action of condenser KZI at each actuation of NS detector Z5l.

The fact that increments of charge are removed from condenser KINS inresponse to NS actuations even during the NS go signal display periodprovides a means whereby those NS vehicles which, under heavy traflicconditions, are stopped by loss of right of way after having actuatedthe NS detector make their presence efiective to increase the next NSinitial interval.

The removal of increments of charge from condenser KINS is accomplishedthru the following circuit including contacts of relay EZ. CondenserKINS is connected to contact e22 of relay EZ thru contact am3 of relayAM in stepping switch positions 2 and 3 and thru contact br2 of relay BRin stepping switch positions 4, 5, 6 and 7. Hence in all of these namedstepping switch positions actuations of NS detector Z5! which operatesrelay EZ will cause contact e22 and e23 to cooperate to remove anincrement of charge from condenser KINS, such charge being transferredto condenser KZI by closure of contact e22 by each actuation andcondenser KZI being discharged by closure of contact e23 betweenactuations.

The charge so removed from condenser KINS by waiting NS trafiic isreplaced thru. resistance RZ5 during the initial interval thus timingsaid initial interval in accordance with the amount of such waiting NStraffic. When condenser KINS is so recharged, i. e. when the NS initialinterval is over, tube YT becomes conductive and condenser KINSdischarges thru relay YR which thereupon operates. The stepping switch,as previously explained, thereupon moves on into position 2, the NS restposition. During the movement of the stepping switch from position I to2 condenser KY is discharged thru driving magnet contact (11113 inpreparation for its use as a timing condenser in stepping switchposition 2.

If the system is not set for normal reversion to the EW lane and thereis no waiting EW traftic the stepping switch will remain in this NS restposition and the NS lane will be continuously accorded the go signaluntil an EW trafiic actuation shall occur.

In stepping switch position 2, the NS go signal rest position; relay YR,tube YT and condenser KY time a predetermined minimum period at the endof which the stepping switch can be moved on into position 3 either byan EW traflic actuation or by normal reversion.

The circuit connecting relay YR, tube YT and condenser KY in steppingswitch position 2 is as follows. Relay YR thru wires 225, 224, wiper W3and position 2 of bank SE3 is connected to condenser KY thru wires 229and 258. In addition a charging circuit is established for condenser KYstarting at grounded power through condenser KY, to wires 258, 229,position 2 of bank S133, wiper W3, wires 224, 223, adjustable resistanceRZI3, wire 2l3, position 2 of bank SE4, wiper W4, wire 226, contact dmlof driving magnet DM to D. 0. plus power.

Wiper W3 is of the non-bridging type so that as the stepping switchmoves from one position to the next there will be no interconnection ofcondenser circuits. Contact dml is included in the charging circuitdescribed above to prevent the plate of tube YT from being charged toflash-over voltage during the instant that condenser KY is disconnectedtherefrom as wiper -W3 moves from one stepping switch position toanother.

The timing of the NS minimum rest position period can be adjusted byregulating resistance RZI3 to control the charging rate of condenser KYin stepping switch position 2.

The grid circuit of tube YT in stepping switch position 2 is connectedthru wire 259, wiper W5 and position 2 of bank SE5, wire 29| topotentiometer PZ5. Wiper W5 is of the bridging type to preventfluctuations in grid potential as the stepping switch moves from oneposition to the next.

It will be noted that the negative end of potentiometer PZ5 ispermanently connected to D. C. minus but the positive end of PZ5 isconnected to ground thru a circuit including wire 254 and contact bm6 ofrelay BM or EW arterial switch Z89. Hence if both switch Z69 and contactbmfi are open the potential of the grid of tube YT will be biasednegative to such a degree that said tube will not break down even thoughplate condenser KY be charged to its maximum positive voltage. Thereforewith contact bmB and switch Z59 open the stepping switch will remain atrest in-position 2 even after condenser KY has become fully charged.

The above condition prevails if the system is not set for normalreversion to the EW lane and there is no waiting EW traffic. Under theseconditions the stepping switch remains in position 2, its NS restposition, and the go signal continues to be displayed in said NS laneuntil the next E:W traffic actuation occurs.

If normal reversion to the EW lane is desired switch Z69 is closed whichwill make the grid potential of tube YT less negative so that the tubewill break down and operate relay YR thus causing the stepping switch tomove from position 2 to 3 as soon as condenser KY is sufficientlycharged, i. e. at the expiration of the stepping switch position 2minimum period. If switch Z69 is not so closed the movement of thestepping switch from position 2 to 3 will take place at any time afterthe expiration of said minimum period upon actuation of the EW detectorZ52 which will deenergize relay BM by opening its holding circuit atcontact fzl of relay FZ. The deenergization of relay BM causes contactb'm6 to complete a circuit connecting potentiometer PZ to ground thusmaking the grid potential of tube YT much less negative so as to causethe tube to break down and relay YR to operate, causing the steppingswitch to move from position 2 to 3. If an actuation of detector Z52takes place before the expiration of the rest position minimum periodsaid stepping switch movement will take place at the end of this minimumperiod.

In stepping switch position 3 the NS go signal. and the EW stop signalremain displayed and three timers, the normal vehicle interval timer,the variable vehicle interval timer and the maximum timer ranconcurrently. The first two of these timers are subject to reset by NSdetector actuations and the timing period of variable vehicle intervaltimer is in addition shortened by waiting EW trafiic in accordance withthe amount of such waiting EW traffic. The maximum timer is not affectedby trafiic in either lane and sets a maximum limit beyond which NStraflic cannot continue to hold the right of way against the cross lane.

The normal vehicle interval timer includes relay YR, tube YT andcondenser KV. The grid of tube YT is in stepping switch position 3connected to potentiometer PZB thru position 3 of bank SB5. The circuitfrom relay YR to wiper W3 of bank SE3 has been traced. Thru this bank,in position 3, condenser KV is connected to relay YR by wires 23!, 232,233 and 234.

Condenser KV, while the stepping switch was in positions I and 2, wasbeing charged thru a circuit including grounded power to condenser KV,wires 234, 233, 232 and 230 to variable resistance RZII, wire 238,contact ar4 of relay AR to positive D. C. power. In stepping switchpositions l and 2 condenser KV was also subject to discharge by NSdetector actuations thru contact e24 of relay EZ, wire 231, contact 1112of relay AR to ground. If, when the stepping switch enters position 3,the traflic in the NS lane has cleared the intersection condenser KVwill have had suflicient time since the last NS detector actuation tobecome fully charged. In stepping switch position 3 condenser KV isconnected to the plate of tube YT via relay YR. Hence if this condenseris fully charged when the stepping switch moves into position 3 tube YTwill immediately break down and operate relay YR to move the steppingswitch on into position 4 with no appreciable stop in position 3. If onthe other hand NS detector actuations have recently discharged condenserKV the normal vehicle interval timer will continue its timing as long asthe stepping switch remains in position 3.

The variable vehicle interval timer includes relay VVR, tube VVT, platecondenser KVV and, in stepping switch position 3, grid condenser KGNS.In stepping switch position 3 plate condenser KVV is charged thru acircuit from grounded power to condenser KVV, wire 263, 26l, 222, Hi,220, variable resistance RZ4, wire 2l2 to position 3 of bank SE4, wiperW4, wire 226, contact dml to D. C. plus power. Wiper W4 is of thenon-bridging type to prevent interconnection of charging circuits duringstepping switch movement. Contact dml is included in this circuit toprevent tube flashover during the stepping switch movement as has beenexplained before.

Condenser KVV is subject to discharge upon actuation of NS detector Z5!thru circuit from the tap wire 3| 1 on potentiometer P2! via wire 350 tocontact arfi of relay AR to contact e25 of relay EZ thru wire 240 whichties into the condenser KVV charging circuit at wire 222. The grid oftube VVT is connected to condenser KGNS thru the circuit including wire249, contact MS of relay BR and wire 246 to condenser KGNS, thence toground. The charge of condenser KGNS has in previous stepping switchpositions been made less negative by the removal of increments of chargeby condenser KBNS, one increment of charge being removed for eachactuation of EW detector Z52, so that the charge on condenser KGNS whenthe stepping switch is in position 3 has been reduced in accordance withthe amount of waiting EW trafl'ic.

The circuits which accomplish the above results are as follows: Instepping switch positions 6 and I condenser KGNS is charged negativelythru the circuit from grounded power to condenser KGNS, wires 246, 241,contact bm5, variable resistor RZ20, wire 255 to potentiometer PZG. Thepoint at which wire 255 makes contact with potentiometer PZ6 fixes themaximum negative potential to which condenser KGNS can be charged bythis circuit. The rate at which this charge takes place can be regulatedby adjusting resistance RZZU.

The removal of increments of charge from the condenser KGNS isaccomplished as follows. In all stepping switch positions condenser KBNSis charged by condenser KGNS and then discharged to a predeterminedpotential once for each actuation of EW detector Z52. This detectoroperates relay FZ whose contacts 126 and is! are effective to accomplishthe above as follows. With contact is! closed condenser KBNS isdischarged to a predetermined voltage thru the circuit includinggrounded power, condenser KBNS, wire 248, contact fz'l, wire 250 topotentiometer PZB. The voltage to which condenser KBNS is so dischargedis regulated by setting the point at which wire 250 contactspotentiometer PZG. A vehicle actuation of EW detector Z52 opens thisdischarge circuit at contact fa! and connects condenser KBNS tocondenser KGNS thru the direct circuit including contact I26. Thevoltage on condenser KBNS, which was regulated to be less negative thanthat of condenser KGNS, will therefore cause the voltage on condenserKGNS to become less negative. Hence, when the stepping switch reachesposition 3 the charge in condenser KGNS will have been reduced inaccordance with the total of all the increments removed by condenserKBNS in response to EW trafiic actuations and substantially inaccordance with the number of such EW actuations since the right of waylast left the EW lane.

The fact that increments of charge are removed from condenser KGNS inresponse to EW trafiic actuations even during the EW go signal displayperiod provides a means whereby those EW vehicles which, under heavytrafiic conditions, are stopped by loss of the right of way after havingactuated the EW detector make their presence felt in decreasing the nextNS variable vehicle interval timingby means which will now be explained.

Since condenser KGN S in stepping switch position 3 acts as the gridcondenser for tube VVT of the variable vehicle interval timer it followsthat the time required for the plate condenser KVV to be charged to avoltage sufficient to cause tube VVT to break down, i. e. the variablevehicle interval, will be decreased substantially in accordance with thereduction of negative charge in condenser KGNS hence substantially inaccordance with the amount of waiting EW traffic.

When tube VVT does break down condenser KVV will discharge thru thistube and relay VVR thus energizing the driving magnet rectifier thrucontact vvr2 and so move the stepping switch on into position 4. At thesame time, thru the opening of contact owl and thru the opening ofcontact mm, which is opened by the operation of the driving magnet DM,both circuits which have previously been traced to the right side of thecoil of relay AM are opened. Therefore relay AM will be released to putin a return right of way call.

When the variable vehicle interval relay VVR so acts to cause thestepping switch movement into position 4, it is obvious that its periodhad been reduced by waiting cross trafilc to less than that of thenormal vehicle interval timer. Hence the right of way return call put inby relay VVR is occasioned by the reduction of the variable vehicleinterval by cross trafiic to less than a predetermined time.

If NS tranic is heavy and NS detector actuations repeatedly reset thenormal vehicle interval time and the variable vehicle interval timer,the maximum timer will after a predetermined time act to move thestepping switch into position 4 and so transfer the right of way fromthe NS lane. The maximum timer consists of relay MXR, tube MXT and platecondenser KMX. In stepping switch position 3 condenser KMX is charged bya circuit from grounded power to condenser KMX, wire 268, thru variableresistance R22 to position 3 of bank SBB thence thru wiper W6 to D. C.plus power. The timing of the maximum period can be regulated by varyingresistance RZZ. When condenser KMX reaches a predetermined voltage tubeMXT will break down and operate relay MXR by discharging condenser KMXthru the circuit from grounded power thru condenser KMX, wires 268, 269,coil of relay MXR, tube MXT, to ground.

The operation of relay MXR causes the stepping switch driving magnetrectifier to be energized thru contact 'mxrZ and so moves the steppingswitch into position 4. At the same time, thru the operation of contactsmazrl and dmZ both circuits previously traced to the right side of thecoil of relay AM are opened. Relay AM is therefore deenergized to put ina NS right of way return call. The fact that the transfer of the rightof way was occasioned by the operation of the maximum timer relay MXRrather than by action of the normal vehicle interval timer indicatesthat a NS detector had been actuated less than the operating period ofthe normal vehicle interval timer, i. e. less than a predetermined time,previous to said transfer of the right of way, which condition it willbe remembered is one under which a return right of way call is put in bythis apparatus.

The deenergization of relay AM causes the return of the right of way tothe NS lane by moving the stepping switch out of the EW rest position 6.This is accomplished as follows.

When relay AM is deenergized back contact amB closes and connects theleft terminal of potentiometer PZ4 to grounded power. When the steppingswitch next reaches position 6 this will cause the grid potential oftube YT, which in this stepping switch position is connected topctentiometer PZ4 thru wire 259, wiper W5 and position 6 of bank SE5 andwire 351, to become less negative thereby permitting tube YT to becomeconductive when its plate condenser KY has been charged to a sufficientvoltage. Condenser KY will thereupon discharge thru relay YR and sooperate relay YR which will cause the driving magnet to move thestepping switch on into position I. This operation was discussed inconnection with the operation of the equivalent timing circuit when thestepping switch was in the NS rest position 2.

A the stepping switch moves from position 3 to 4 condenser KY isdischarged thru driving magnet contact dm3, condenser KVV is dischargedthru contact (11114 and condenser KMX is discharged thru contact ($1125to prepare them for timing their next intervals.

In stepping switch position 4 the NS go signal is extinguished and theNS amber signal is illuminated. To accomplish this change relay BR isenergized thru wiper W2 and position 4 of bank SBZ. Contact 111'! ofrelay BR being thereby closed light relay BLR is operated whichextinguishes the NS go signal Z by opening contact blrl and illuminatesthe NS amber signal Z46 by closure of the contact blr2.

While the warning or stop signal i being displayed in the NS lane,stepping switch in position 4, 5, 6, l or 8, relay AM, as previouslyexplained, depends for its current on a holding circuit which includescontact eel of relay EZ. Therefore thru the opening of contact eel relayAM will be deenergized by a NS vehicle actuation occurring during the NSwarning or stop signal display period. Relay AM will thereupon functionto call the right of way to the NS lane in the manner previouslyexplained.

The NS amber or warning period, stepping switch in position 4 is timedby relay YR, tube YT and condenser KY which is connected to platecircuit of tube YT thru relay YR and wiper W3 and position 4 of bankSE3.

Condenser KY is charged during this period thru a circuit from groundedpower to condenser KY, wires 258, 229, position 4 and wiper W3 of bankSE3, wire 224, 223, variable resistance RZI,

wire 2| l, position 4 and wiper W4 of bank SE4, wire 226, contact dml toD. C. plus. The duration of the NS amber period can be regulated byadjusting resistance RZI to control the charging rate of condenser KYduring this period. The grid of tube YT i connected to potentiometerPZG. When condenser KY is charged to a predetermined voltage tube YTwill become conduc tive and discharge the energy of condenser KY thrurelay YR thus operating the driving magnet DM to move the steppingswitch into position 5.

Stepping switch positions 5, 6, I and 8 correspond respectively topositions I, 2, 3 and 4 except that the go signal or the amber signal isbeing displayed to the EW lane instead of the NS lane and the functionsof the NS and EW detectors are in general interchanged so that EWactuations tend to extend the timing periods while the NS actuationstend to decrease them.

In stepping switch position 5 relay AR is unoperated hence the NS stopsignal Z41 is illuminated thru contact alrl and the EW go signal Z48 isilluminated thru contacts blr4 and alr3. The EW stop signal Z50 isextinguished by the opening of contact alrZ. i

The EW initial interval, stepping switch in position 5, is timed byrelay YR, tube YT and condenser KIEW just as the NS initial interval istimed by the same relay and tube cooperating With condenser KINS.Condenser KIEW has been prepared for timing the EW initial interval inaccordance with the waiting EW traflic by having its initial charge,introduced during the last EW go signal period thru contact bm4 andresistance RZ I 6, decreased during and subsequent to this chargingperiod by the removal of charge increments by condenser KZ2 in responseto EW actuations, just as condenser KINS was prepared to time the NSinitial interval.

The removal of increments of charge from condenser KIEW by condenser KZ2is accomplished thru contacts fzZ and 23 of relay FZ. During the EWinitial interval condenser KIEW is recharged thru the circuit fromground to condenser KIEW, wire 283, position and wiper W3 of bank SE3,wires 224, 223, 2|0, variable resistance RZIO, wire 2l5, position 5 andwiper W4 of bank SB4, wire 226 and contact dml to D. C. plus power. Atthe end of the EW initial interval, condenser KIEW having beenrecharged, tube YT becomes conducting and permits condenser KIEW todischarge thru wire 283, position 5 and wiper W3 of bank SB3, wires 224,225, coil of relay YR and tube YT to ground. Relay YR thereupon operatesand the stepping switch moves on into position 6, the EW rest position.

When the stepping switch is in position 6 relay BM is operated. Thecircuits and functions of this relay are similar to those of relay AMexcept that they apply in general to the EW lane instead of the NS lane.It has an operating circuit from grounded power thru wiper WI andposition 6 of bank SBI wires 209, 208, coil of relay BM, wires 201, 216,211, 221, contact dm2 to A. C. plus power. When relay BM operates anadditional source of A. C. plus power thru a holding circuit independentof contact (11122 is connected to the left side of the coil of relay BMthru wire 201, 216, 218, contact bm2, wire 219, contact macrl andcontact vvrl to A. C. plus power.

When relay BM operates an additional source of grounded power isconnected to the right side of the coil of relay BM thru wire 208,contact bml and fzl thence to grounded power. These last two describedadditional circuits taken together constitute a holding circuit similarto that previously described in connection with relay AM. The conditionsunder which this holding circuit will be broken to deenergize relay BMand so call the right of way to the EW lane are similar to thoseefiective in the case of the corresponding holding circuit associatedwith relay AM and will be described in detail later.

In stepping switch position 0, the EW rest position, relay YR, tube YTand condenser KY cooperate to time a minimum period at the expiration ofwhich the stepping switch can be moved on into position 1 by normalreversion if NS arterial switch Z68 is closed or by an actuation of NSdetector Z5l just as it is moved into position 4 if switch Z69 is closedor EW detector Z52 is actuated. In stepping switch position 6 the timingcircuit is substantially the same as that effective in position 2 exceptthat condenser KY is charged thru variable resistance RZI4 instead ofvariable resistance RZI3 and that the grid of tube YT is connected topotentiometer PZ4 instead of PZ5 thereby making the movement of thestepping switch out of position 6 dependent upon NS arterial switch Z68or NS trafilc thru deenergization of relay AM instead of EW arterialswitch Z69 or EW traffic deenergization of relay BM.

In stepping switch position 1, the EW traflic timed position, the normalvehicle interval timer, the variable vehicle interval timer and themaximum timer, run concurrently just as they did in the correspondingstepping switch position 3, the NS traflic timed position. The chargingcircuit for condenser KV of the normal vehicle interval timer instepping switch position 1 includes variable resistance RZ I 8 insteadof variable resistance RZI'I which was in this circuit in steppingswitch position 3. Likewise in the variable vehicle interval ,timercondenser KVV charging circuit resistance RZ9 replaces the correspondingresistance RZ4 and in the maximum timer condenser KMX charging circuitresistance RZ1 replaces the corresponding resistance RZ2. Thesubstitution of these resistances permits the timing of thecorresponding NS and EW intervals to be independently adjusted.

In stepping switch position 1 condenser KGEW is included in the gridcircuit of variable vehicle interval timer tube VVT in place ofcondenser KGNS which was attached to the grid of tube VVT in steppingswitch position 3. Grid condenser KGEW, while the stepping switch is inNS go positions 2 and 3, is charged negatively thru the circuit fromgrounded power to condenser KGEW, wires 245, 244, contact (11115,variable resistance RZIS, wire 256 to potentiometer resistance PZG.

During and subsequently to the above charging period the negative chargein condenser KGEW is decreased by the withdrawal of an increment ofcharge by condenser KBEW thru the operation of contacts e26 and e21 ofrelay EZ, at each NS detector actuation in order to decrease the EWvariable vehicle interval in accordance with the amount of waiting NStraific just as the NS variable vehicle interval was decreased inaccordance with the amount of waiting EW traific thru the removal ofnegative charges from condenser KGNS by condenser KBNS thru contacts I26and 1'21 which has been previously explained.

As the stepping switch leaves position 1, if this movement is occasionedby variable vehicle interval timer relay VVR or by maximum timer relayMXR, relay BM will be deenergized to put in a call for the return of theright of way to the EW lane just as relay AM was deenergized if eitherof these relays moved the stepping switch from position 3 to 4, whichhas previously been described. This deenergization of relay BM willresult from the removal of A. C. plus power connections from its coilthru the opening of its holding circuit at contact curl of relayVVR orcontactmxrl of relay MXR and the opening of its operating circuit atcontact (21122, both of which circuits have been traced from A. C. pluspower to the left side of the coil of relay BM.

If the stepping switch movement from position 1 to 8 is on the otherhand occasioned by the operation of the normal vehicle interval timerrelay YR relay BM will not be deenergized and hence no EW return rightof way call will be put in.

In those stepping switch positions in which the warning signal or thestop signal is being displayed to the EW lane that part of the relay BMoperating circuit including bank SBI is open at this bank and thepreviously described parallel holding circuit including contact fzl ofrelay FZ and bml of relay BM becomes the sole supply of current to theright side of the coil of relay BM. The first EW detector actuationduring the EW stop or warning signal display period will open thisholding circuit at contact fzl and deenergize relay BM thereby puttingin a call for the return of the right of way to the EW lane. Said returnof the right of way will be occasioned by back TREC SIGN/RUNS.

Search than grid of tube YT so that tube YT will break down 5 when itsplate condenser becomes sufliciently charged and operate relay YR tocarry the stepping switch out of the said NS rest position.

Stepping switch position 8 is the EW amber or warning period position.Relay BB. is ener-, 10

gized in this position thus deenergizing light relay, BLR also. Sincerelays AR and ALR are also deenergized in this stepping switch positionthe EW go signal Z48 will be extinguished by the opening of contact M14and the EW amber signal 15 Z49 will be illuminated thru the closure ofcontact 12213.

The duration of the EW amber period is timed by relay YR, tube YT andcondenser KY just as the NS amber period was timed by them except thatcondenser charging resistance RZ6 replaces resistance RZl so that thetiming of the EW and NS amber periods can be independently adjusted.When relay YR operates, driving magnet DM moves the stepping switch intoposition I at the same time discharging condenser KY thru contact dm3 toprepare it for timing subsequent intervals. This completes the signaldisplay cycle.

To summarize briefly, intervals are timed as follows by the apparatus ofthe embodiment of my invention shown in Figs. 2 and 3.

The NS initial interval, stepping switch in position I, is timed byregular charging of condenser KINS which has previously been subject tothe removal of unit charges by NS traffic actuations. The replacement ofthese removed charges times this period in accordance with the amount ofsuch waiting NS traffic.

The EW initial interval, stepping switch in position 5, is timedsimilarly by condenser KIEW from which unit charges have previously beenremoved by EW traflic.

The NS traific timed right of way period, stepping switch in position 3,is timed concurrently by three timers, the normal vehicle intervaltimer, the variable vehicle interval timer, and the maximum timer.

The NS normal vehicle interval is timed by regular charging of condenserKV subject to reset discharge by NS trafic actuations. This condenser isbeing so charged and discharged in stepping switch position 2, the NSrest position, so that the normal vehicle interval timer will beefiective to move the stepping switch out of position 3 into position 4thus transferring the right of way without delay if all NS trafiic hascleared the intersection when the stepping switch moves into position 3.

The NS variable vehicle interval is timed by regular charging ofcondenser KVV which, in stepping switch position 3, is subject to resetdischarge by NS traific actuations. At the same time the period of thevariable vehicle interval timer is governed by the charge in condenserKGNS which has been previously regulated in accordance with EW trafficactuations.

The EW traffic timed right of way period, stepping switch in position 1,is similarly timed by the same three timers. However, in the variablevehicle interval timer condenser KGEW replaces condenser KGNS so thatthe period of the variable vehicle interval timer when timingthe EW lanewill be governed by waiting NS traffic.

Now considering the present invention as applied to one embodiment ofthe aforesaid copending application, two additional gas discharge tubesDT and ET of the grid controlled type similar to tube VVT are connectedwith the anodes and cathodes in parallel with the anode and cathoderespectively of tube VVT, so that tubes DT and ET each serve in additionto tube VVT as elements responsive to a particular level of charge andcorresponding voltage on condenser KVV in timing the variable vehicleinterval.

As will now be explained each tube has its grid bias individuallyadjusted in accordance with certain trafiic or other conditions todetermine the level of charge on condenser KVV at which theanode-cathode circuit of the tube will become conducting to operaterelay VVR by discharge of condenser KVV, and thus to operate steppingmagnet DM and step the stepping switch from the right of way positionfor the lane for which the variable vehicle interval or traffic timedinterval is being timed. Since all three tubes VVT, DT, and ET areconnected to be controlled by condenser KVV to operate relay VV'R,whichever tube has its grid bias adjusted to the lowest value to makeits break down voltage for conduction lowest will become conducting tooperate relay VVR, as the voltage on condenser KVV increasesprogressively in its timing action.

The grid bias of tube VVT is reduced progressively by a small amount foreach of a series of actuations by traffic arriving (and waiting) againsta stop signal as described above, and this is one of the features of thecopending application.

The grid bias of tube DT is reduced progressively by a small amount foreach of a series of actuations by trafiic moving with the go signal, inaccordance with one feature of the present invention, these latteractuations being the same traflic actuations which momentarily dischargecondenser KVV to reset its timing action to prolong the go signalperiod. Between such actuations the grid bias of tube DT is increasedgradually, tending to restore it to the original value it had before thereduction in bias by actuations.

Since reduction of the grid bias reduces the break down voltage for theanode-cathode circuit of the tube, the latter will become conducting tooperate relay VVR at a lower level of charge on timing condenser KVV andthus will reduce the variable vehicle interval timed by the gradualrecharging of condenser KVV from each actuation by trafiic having rightof way. Thus the right of way will be terminated on occurrence of asmaller time gap between vehicles than would have been initially thecase before such reduction of grid bias.

The reduction of grid bias on tube DT by traffic moving on the g0 signalis provided as follows. Assume that the stepping switch is in the NStrafiic timed position 3 in which the green signal is displayed to NSand the red signal is displayed to EW, and in which relay AR (Fig. 2) isin energized position and relay BR is in deenergized position. In thisposition the grid of tube DT has initially a relatively high biasprovided by its connection via small limiting resistance RX2, wires 3l9,348, contact br'l of relay BR, wire 3, control resistance RZZI, wire32'! to potentiometer PZ6. Condenser KD is connected via resistance RXZand wire 3I9 between the grid of tube DT and the ground wire, to

which the cathode of tube DT is also connected, and serves to controlthe grid bias potential.

This condenser is of large capacity (of the order of mid. for example).Upon actuation of the NS trafiic detector Z5| in position 3 of thestepping switch the relay EZ will be energized momentarily and at itscontact e28 will connect a small condenser KDNSI for example tocondenser KD to reduce the charge and negative potential in condenser KDby a small increment. This occurs by circuit from ground wire via wire345, condenser KDNSI, wire 3|5, limiting resistance RX3, contact e28,wires 3l6, 3", contact brl, wire 348, condenser KD to ground wire.

Relay EZ is deenergized again after each momentary actuation and in itsdeenergized position via contact e29 connects condenser KDNSI via wire3| 3 to a point on potentiometer PZG nearer ground to dischargecondenser KDNSI. Thus with each trafiic actuation a small increment ofcharge is removed from condenser KD by small condenser KDNSI. Thisreduces the bias potential of the grid of tube DT and makes the laterresponsive to a lower potential on the main variable vehicle intervaltiming condenser KVV.

Between such actuations the circuit from condenser KD via the controlresistance RZ2I to a high negative point on potentiometer P26 willgradualy recharge condenser KD at a relatively slow time rateproportional to capacity of condenser KD and inversely proportional tothe size of resistance RZZI and thus will tend to restore the grid biason tube DT to its initial value.

An auxiliary condenser KDNS2 similar to KDNSI is provided for connectionin parallel with KDNSI by switch 343 to increase the increment of chargeremoved from condenser KD with each trafiic actuation if desired. Switch343 is set in one position or the other manually to balance theactuation effect on the grid bias for two and four lane streets, forexample. A similar arrangement may be used to provide adjustablecapacity for condensers KBNS and KBEW for example, and is useful incompensating for differences in the number of non-interfering lanesreceiving right of way simultaneously at different types of streetintersections.

With the stepping switch in the EW traflic timed position I in which thegreen signal isdisplayed to EW and the red signal to NS, relay AB, is inits deenergized position and relay BR is in energized position, and thegrid of tube DT is connected via resistance RXZ and wire 3 Hi tocondenser KD as before but is now disconnected from the lower contacthr! of relay BR and is connected with the upper contact M6 to place thegrid under control of EW trafiic. EW traflic actuations momentarilyenergize relay FZ and at contact 128 remove small charges from condenserKD by means of the small condenser KDEWI. Each energization of relay FZdisconnects condenser KDEWI from wire 314 connecting with low point onpotentiometer PZG,

and connects KDEWI with condenser KD via the limiting resistance RX4,contact fz8, contact D16, and wire 348 to remove a small charge fromcondenser KD. Successive actuations will successively reduce the chargeon condenser KD and thus ping switch is connected via wire 3 48 andcontact M6 and control resistance RZ22 and wire 320 to a high bias pointon the potentiometer PZS.

In accordance with another feature of the present invention the gridbias of another tube ET is reduced at a slow time rate to reduce thevehicle interval gradually during the right of way period. In thepreferred arrangement with switches 338 and 334 closed as shown in Fig.3, this slow reduction of the grid bias to reduce the vehicle intervalis under control of the respective relays AM and BM which are releasedresponsive to trafiic approaching a red signal and begins with thearrival of the first vehicle to wait against the stop signal on thestreet not having right of way. In an alternative arrangement which maybe desirable in some circumstances, one or the other or both switches334 and 338 may be set in their open position and the timed gradualreduction of the grid bias of tube ET and the consequent reduction ofthe vehicle interval will proceed throughout the right of way periodWithout waiting for the first vehicle to arrive against a red signal.With only switch 338 open the timed reduction of the EW vehicle intervalstarts automatically at the beginning of the EW green period and timedreduction of the NS vehicle interval is dependent upon EW vehicleactuation. With only switch 334 open the timed reduction of the NSvehicle interval starts automatically with NS green but timed reductionof the EW vehicle interval is dependent on NS vehicle actuation. Withboth switches open the timed reduction of vehicle interval on eachstreet will start automatically with the green on that street.

The timed reduction of grid bias of tube ET is provided as follows.Condenser KE is connected between ground and the grid of tube ET vialimiting resistance RX5. Condenser KE controls the grid potential oftube ET in connection with one or another of the control resistancesRZ23 and RZ24 and its capacity is selected with respect to these highresistances to serve as a timing condenser in controlling grid voltagebias reduction. In the NS vehicle interval position 3 of the steppingswitch, relay AB. is energized and relay BR is deenergized. Assumeswitches 338 and 334 closed as shown in Fig. 3, and assume that notraflic is yet waiting on the EW street, and relay BM is thereforeenergized as described above. Then condenser KE and the grid of tube ETare connected via limiting resistance RX5, wire 325, contact br9 ofrelay BR, contact bm'l, wires 335 and 336 to a high bias point onpotentiometer PZB which maintains the grid at its initial bias.

Now if an EW vehicle arrives, and starts waiting against the red signalbeing displayed to the EW street, the relay BM will be deenergized andwill remain deenergized since its original operating circuit is open andits lock in circuit is now also open as described above. The contact bmlwill now therefore be open and the connection of the grid and condenserKE with the high bias point on the potentiometer PZ6 will beinterrupted, thus rendering effective the branch circuit from condenserKE and the grid via br9, wire 332, control resistance RZ24 and wire 340to a relatively low bias point on potentiometer PZB. This allowscondenser KE to discharge slowly at a time rate determined by thecontrol resistance RZ24, and thus gradually reduces the grid bias oftube ET and correspondingly reduces the NS vehicle interval whichdetermines the maximum limiting gap in traflic at which NS ELEQTWI SHSNRUNS trafiic will yield right of way to the waiting EW trafic. Since thetimed slow reduction of the grid bias of tube ET for the NS vehicleinterval was initiated by the arrival of the first waiting vehicle onEW, and proceeds at a predetermined time rate in accordance with thewell known discharge characteristic of a condenser, the consequentreduction in the NS vehicle interval is substantially in accordance Withthe length of time any EW traffic has been waiting for right of way.

After termination of NS right of way and shift of the stepping switch toNS amber position 4, relay AR remains energized and relay BR becomesenergized as will be noted by reference to banks SBl and $32 of thestepping switch. In this position the grid control condenser KE isrestored to a high bias voltage again as a starting point for control ofthe EW vehicle interval in the following EW right of way period, thisrestoration being accomplished by connection of condenser KE via wire325, contact D18, wire 328, contact M9, and wire 33'! to a high biaspoint on potentiometer PZB.

In the EW trafiic time interval, stepping switch position 1, the relayAB is deenergized and relay BR is energized, and the grid controlcondenser KE is connected via wire 325, contact br8, wires 326, 321, andcontrol resistance RZ23 and wire 3 to a low point on potentiometer PZ6.Assuming switch 338 closed as shown in Fig. 3, the circuit justdescribed is inefiective in absence of NS traffic actuation since it isshunted by a circuit via wire 328, 329, switch 338, contact MM, and wire33'! to a high point on potentiometer PZB. Upon NS traffic actuationhowever, relay AM is deenergized and remains deenergized as describedabove, and contact am? opens to interrupt the shunting circuit and thuspermit condenser KE to discharge slowly at its characteristic time ratethrough control resistance R223. As condenser KE gradually dischargesduring the EW right of way period the EW vehicle interval is reducedcorrespondingly in a manner similar to that described in connection withthe NS vehicle interval reduction.

Fig. 4 shows th condenser KD and tube DT and associated apparatusprovided in accordance with the feature of the present invention ofreducing the vehicle interval or gap limit interval by closely spacedtraffuc having the right of way, or by what might be termed the volumeor density of traffic having right of way. In this figure the tube WTand associated grid control condensers KGNS and KGEW and unit chargeremoving condensers KBNS and KBEW are omitted, as are also the tube ETand grid control condenser KE and associated circuits. Fig. 4 should beviewed in conjunction with Figs. 2 and 3, except for the apparatus whichmay be omitted or disregarded as above noted, for the purpose ofconsidering a complete cycle of operation of the apparatus as part of aright of way traffic control system, but Fig. 4 illustrates particularly the apparatus and circuits providing reduction of the vehicleinterval for right of way by trafiic having the right of way as one ofthe features of the present invention, together with repetition ofcertain elements and circuits common with Fig. 3 and with the disclosureof the copending application, such as th vehicle interval timingcondenser KVV and traffic actuated reset circuits via contacts 625 andfz5 therefor, the VVR relay coil, and the stepping switch bank SE4 whichconnects the charging circuits via control resistances R24 and RZ9 tocondenser seats noon KVV to time the vehicle interval in the NS and EWtrafiic timed positions of the stepping switch cycle. The potentiometerPZ6PZ'I and the circuit via contact dmd for resetting condenser KVV instepping from one position to the next by action of stepping magnet DMare also repeated from Fig. 3, and. it will be understood that in thetrafilc timed positions 3 and 'l the operation of relay VVR by dischargeof condenser KVV through tube DT upon completion of vehicle intervaltiming during a gap in traflic will energize stepping magnet DM and stepthe stepping switch wipers to the next position to continue operation ofthe signal cycle, as described above in connection with Figs. 2 and 3.

It is believed that reference to Fig. 4 in connection with the precedingdescription of operation of the grid control of the grid of tube D'I' bycondenser KD and the related circuits will assist in an understanding ofthe novelty of this feature of the invention and will serve toillustrate how these features may be employed alone to reduce thevehicle interval if desired, without the feature of the copendingapplication of reduction in accordance with amount of traflic waiting asprovided by tube VVT, and without the feature of the present inventionof the reduction of the vehicle interval in accordance with the lengthof time of right of way or of traflic waiting.

The apparatus particularly concerned with the last mentioned feature isshown in Fig. 5, which like Fig. 4, also repeats certain of the otherc0mmon apparatus from Fig. 3 to permit the complete operation of thevehicle interval timing device to be viewed separately as controlled bythe timing action of condenser KE on the reduction of grid bias of tubeET. It is believed that Fig. 5 will assist in an understanding of theindividual novelty of this latter feature of the invention.

The reference legends and general layout of the parts of Figs. 4 and 5are the same as that of the corresponding parts of Figs. 2 and 3 so thatthe operation of the parts and circuits can readily be followed byreference to the description of the corresponding parts of Figs. 2-3.

It will be understood that insofar as the features of the inventionillustrated in Figs. 4 and 5 are concerned it is not essential that theinitial interval be varied in accordance with the amount of tralficwaiting as described above in connection with Figs. 2 and 3 and that apredetermined initial interval might be employed for each street forexample or the initial interval might be omitted entirely as a separatepart of the cycle by making the reduction of the vehicle interval inaccordance with one or another feature of the invention quite extensive,starting with a sufficiently long vehicle interval at the beginning ofthe right of way period to serve to permit standing traffic to get intomotion, and then reducing this vehicle interval progressively at arather rapid rate early in the right of way timing period by the vehicleinterval timer, with a slower reduction as the right of way period isprolonged progressively by moving trafiic, along the lines of thetapering off of the discharge curve of the grid control condensers. Inapplying the inven-- tion in this manner however the vehicle detectorswould preferably be set nearer to the intersection for most efficientresults.

In the preferred embodimentof my invention however the initial intervalis preferably automatically varied in accordance with amount of waitingtraflic as described in connection with Figs. 2 and 3, for improvedefficiency of operation.

The present invention may be employedwith advantage in combination withthe apparatus of the copending application to obtain a markedcoordination of timing of the signals at a series of intersections alonga street or through a group of intersections forming a grid of which asmall part is illustrated in Fig. 6 for example, without interconnectionor forced resynchronization of any kind. The feature of the reduction ofvehicle interval in accordance with the density of. moving traflichaving the right of way as illustrated in Fig. 4 is of particularadvantage in this regard in combination with the feature of reduction ofvehicle interval in accordance with the amount of traflic arrivingagainst a red signal. If it is desired to emphasize this coordinationeffect the trafiic detectors are preferably set back further from theintersection than would be the case for control of the intersection asan isolated unit, in order to enable the control mechanism to reduce thevehicle interval in accordance with the approach of a considerable groupor fleet of vehicles against the red signal before any considerable partof such group reaches the intersection and is required to stop.

With proper spacing of signalized intersections and trafiic speed inrelation thereto the traffic may be organized into fleets of vehiclestraveling through the series of intersections progressively with thegreen signal periods appearing to travel along the street in eitherdirection, the gaps appearing between fleets of vehicles matching thered periods on the common street to permit the cross streets to receivethe green signal.

The apparatus of Fig. 4 aids in recognizing promptly the end of the mainfleet of vehicles in any group since the closely spaced vehicles in thefleet will progressively reduce the vehicle interval setting a gap limitprogressively closer to the actual gap between vehicles in the fleet andas soon as the main fleet has passed, the spacing of vehicles willincrease rather rapidly and the right of way will be terminated promptlyand transferred to traffic on the cross street.

In the combined apparatus of Figs. 2 and 3 it may be desirable incertain instances to reduce the vehicle interval almost to zero in orderto prevent traflflc practically from holding right of way any longeragainst opposing traflic, in place of a separate overall maximum rightof way timing circuit and tube and condenser for example, or responsiveto a preferred vehicle such as a street railway car for example by meansof a separate relay corresponding to AM or BM for actuation by suchvehicle to connect condenser KE effectively through a relatively lowresistance to a very low bias point on potentiometer PZ6.

For the purpose of permitting such drastic reduction of the vehicleinterval either rapidly or gradually, when desired, the presentembodiment resets the vehicle interval timing action by discharging thecondenser KVV to a predetermined value considerably above completedischarge and determined by the tap 3 on potentiometer PZ'I and wire 3|2connecting with the ballast condenser KX. The stepping switch magnet DMresets condenser KVV by contact dm4 and a limiting resistance and theconnection with condenser KX and the tap 3 on potentiometer PZl, and thetraffic actuated reset of condenser KVV to prolong right of way isconnected via contact e25 and contact art; or via contact fz5 andcontact ar1, through wire 350 to the tap 3! l.

In my preferred embodiment I have found it satisfactory to employ atotal D. C. voltage of about 450, that is across PZl and PZB together asone potentiometer, with about 400 volts on P2! and about 50 volts on PZBwhich serves to control the negative bias voltage on the grids of tubesVVT, YT, DT, and ET. For these tubes I have found an operating range ofabout to 400 volts satisfactory on the anode-cathode circuits and aratio of break-down voltage to grid bias of about 10 to 1. The timingand grid control condensers KV, KY, KMX, KINS, KIEW, KGNS, KGEW, KVV,KD, and KB may preferably be of 5 mid. capacity and the controlresistances of the order of 200,000 ohms per second of time desired, forexample. The condensers KBNS, KBEW, KZI, KZZ, KDNSI, KDNSZ, KDEWI, andKDEW2, may preferably be of the order of 0.1 to 0.4 mfd., the capacityof these condensers depending upon the number of parallel traffic laneson the streets and the degree of effect desired to be obtained for eachtrafiic actuation in connection with the several circuits for removingcharges from the main condensers by small unit charges responsive totrams actuations.

It will be appreciated that while the apparatus disclosed representspreferred embodiments of my invention considerable modification may bemade in the values of the electrical elements, in the design andarrangement of the several parts and substitution of equivalent partsand circuits by those skilled in the art Without departing from thespirit of the invention as defined by the claims.

Iclaim:

1. In a traffic control apparatus for according right of waysuccessively to each of a plurality of interfering traffic lanes, meansresponsive to each of a plurality of traffic units in one lane duringright of way accord therein to prolong such right of way for a smallincrement of time, and further means to reduce the length of saidincrement responsive to closely spaced such traffic units.

2. In a traiiic control apparatus for according right of waysuccessively to each of a plurality of interfering tramc lanes, meansresponsive to each of a plurality of traffic units in one lane duringright of way accord therein to prolong such right of way for a smallincrement of time, and further means responsive to such traffic units insaid one lane to adjust the length of said increment substantially inaccordance with the time spacing between such trafiic units.

3. In a traffic control apparatus for according right of waysuccessively to each of a plurality of interfering traflic lanes, meansresponsive to each of a plurality of traffic units in one lane duringright of way accord therein to prolong such right of way for a smallincrement of time, and means responsive to traffic in another of saidlanes during right of way accord in said one lane to reduce saidincrement gradually in accordance with the length of time such trafficin said other lane has been waiting for accord of right of way.

4. In a traffic control apparatus for according right of waysuccessively to each of a plurality of interfering trafiic lanes andhaving means responsive to each of a plurality of traflic units in onelane during right of way accord therein to prolong such right of way fora small increment of time, the combination of three concurrently actingtiming means for timing independently adjustable time intervals fordetermining the length of said increment of right of way prolongation,the first such means acting to reduce its time interval progressivelyresponsiVe to the number of units of trafiic on another of said laneswaiting for right of way, the second such means acting to reduce itstime interval gradually responsive to the length of time any traific hasbeen waiting for right of way on said other lane, and the third suchmeans acting to reduce its time interval responsive to close spacing ofmoving trafiic units in said one lane having right of way, and meansresponsive to each of a plurality of traffic units in said one laneduring right of way accord therein to reset all three of said timingmeans substantially simultaneously to retime their intervalsconcurrently.

5. In a trairlc control apparatus for according right of waysuccessively to each of a plurality of interfering traffic lanes andhaving means responsive to each of a plurality of trafiic units in onelane during right of way accord therein to prolong such right of way fora small increment of time, the combination of two concurrently actingtiming means for timing independently adjustable time intervals fordetermining the length of said increment of right of way prolongation,the first of such two means acting to reduce its time intervalprogressively responsive to the number of units of trafiic on another ofsaid lanes waiting for right of way, the second such means acting toreduce its time interval gradually responsive to the length of time anytraffic has been waiting for right of way on said other lane, and meansresponsive to each of a plurality of traffic units in said one laneduring right of way accord therein to reset both of said timing meanssubstantially simultaneously to retime their intervals concurrently.

6. In a trafic control apparatus for according right of way successivelyto each of a plurality of interfering traflic lanes and having meansresponsive to each of a plurality of traflic units in one lane duringright of Way accord therein to prolong such right of way for a smallincrement of time, the combination of two concurrently acting timingmeans for timing independently adjustable time intervals for determiningthe length of said increment of right of way prolongation, the first ofsuch two means acting to reduce its time interval progressivelyresponsive to the number of units of traflic on another of said laneswaiting for right of way, and the second such means acting to reduce itstime interval responsive to close spacing of moving trafiic units insaid one lane having right of way, and means responsive to each of aplurality of traffic units in said one lane during right of way accordtherein to reset both of said timing means substantially simultaneouslyto retime their intervals concurrently.

7. In a trafiic control apparatus for according right of waysuccessively to each of a plurality of interfering traffic lanes andhaving means responsive to each of a plurality of traffic units in onelane during right of way accord therein to prolong such right of way fora small increment of time, the combination of two concurrently actingtiming means for timing independently adjustable time intervals fordetermining the length of said increment of right of way prolongation,the first of such two means acting to reduce its time intervalresponsive to close spacing of moving trafiic units in said one lanehaving right of way, and the second such means acting to reduce its timeinterval gradually re- Search Rant sponsive to the length of timetraflic has been waiting for right of way on said other lane, meansresponsive to each of a plurality of trafiic units in said one laneduring right of way accord therein to reset both of said timing meanssubstantially simultaneously to retime their intervals concurrently.

8. In a traffic control apparatus for interfering traffic lanes havingright of way signals for the respective lanes, trafiic actuated devicesfor the respective lanes, and a control mechanism for operating saidsignals responsive to actuation of said devices, said control mechanismincluding a timer operated during operation of the right of way signalfor one lane to provide a time interval and adapted to be reset torepeat its time interval, means connecting said timer to the trafiicactuated device for said one lane having the right of way signaloperated therein to so reset said timer responsive to trafiic actuation,means operated by said timer at completion of its time interval inabsence of such resetting actuation to operate said control mechanism toterminate operation of the right of way signal in said one lane andtiming means for reducing progressively the time interval of said timerduring operation of the right of Way signal on said lane.

9. In a traffic control apparatus for interfering 'trafiic lanes havingright of way signals for the respective lanes, traffic actuated devicesfor the respective lanes and a control mechanism for operating saidsignals responsive to actuation of said devices, said control mechanismincludinga timer operated during operation of the right of way signalfor one lane to provide a time interval and adapted to be reset torepeat its time interval, means connecting said timer to the trafficactuated device for said one lane having the right of way signaloperated therein to so reset said timer responsive to trafiic actuation,means operated by said timer at completion of its time interval inabsence of such resetting actuation to operate said control mechanism toterminate operation of the right of way signal in said one lane andtiming means for reducing progressively the time interval of said timer,when operated, and means connecting said timing means to the traflicactuated device of said another lane to operate said timing means byactuation of the last named device.

10. In a traffic control apparatus for interfering traflic lanes havingright of way signals for the respective lanes, traffic actuated devicesfor the respective lanes and a control mechanism for operating saidsignals responsive to actuation of said devices, said control mechanismincluding a timer operated during operation of the right of way signalfor one lane to provide a time interval and adapted to be reset to'repeat its time interval, means connecting said timer to the trailicactuated device for said one lane having the right of way signaloperated therein to so reset said timer responsive to traflic actuation,means operated by said timer at completion of its time interval inabsence of such resetting actuation to operate said control mechanism toterminate operation of the right of way signal in said one lane andmeans operating responsive to actuation of the traffic actuated deviceon said one lane during operation of the right of way signal therein toreduce progressively the time interval of said timer.

11. In a trafilc control apparatus for interfering traffic lanes havingright of way signals for

